Turbine blade with reverse cooling air film hole direction

ABSTRACT

A gas turbine engine includes turbine blades having film cooling holes at an outer face of an airfoil wherein the film cooling holes are designed to be better filled with air. In a disclosed embodiment, the film cooling holes include a meter section extending along a direction having a main component extending from a blade tip to a blade root. In addition, a diffused section communicates with the meter section at a face of the airfoil. The diffused section is spaced toward the blade tip from the meter section. In this manner, centrifugal force ensures the diffused section is also filled with air.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/651,226, which was filed Jan. 9, 2007.

BACKGROUND OF THE INVENTION

This application relates to a turbine blade, wherein the meter sectionsof film cooling holes extend at an angle and in a direction toward ablade root from the blade tip. In addition, a diffused section of a filmcooling hole extends toward the blade tip from a meter section toreceive air driven by centrifugal force.

Gas turbine engines are known, and include a plurality of sections whichare typically mounted in series. Typically a fan delivers air to acompressor. Air is compressed in the compressor and delivered downstreamto be mixed with fuel and combusted in a combustor section. Products ofcombustion move downstream over turbine rotors. The turbine rotorsinclude a plurality of removable blades which rotate with the rotors,and are driven by the products of combustion. The turbine rotors drivecomponents within the gas turbine engine, including the fan andcompressor.

The turbine blades become quite hot from the products of combustion.Thus, it is known to pass cooling air through internal cooling passageswithin the turbine blades. In one known cooling technique, air is passedoutwardly through holes on an outer face of an airfoil of the turbineblade, such that the cool air passes along the outer face. These filmcooling holes are designed to maximize the coverage surface area on theblade, which receives the air and also to maximize the time cooling airis kept on a face of the blade.

In the prior art, the film cooling holes have a meter section thattypically extend at an angle to the outer face. The angle includes amajor component in a direction extending from a blade root and toward ablade tip. In addition, a diffused section extends back from this metersection towards the blade root. This type of film cooling holes is knownas shaped or flared holes. The purpose of the diffused section is toslow the speed of the cooling air down as it reaches the face of theblade, such that the air would be less likely to move away from theface, and more likely to move along the face.

However, in the prior art, a centrifugal force applied as the bladerotates, moves the cooling air radially outwardly and toward the bladetip. Thus, the diffused section tends not to be filled with air. Thiscentrifugal force and flow momentum drives the air into the radiallyouter portions of the holes spaced toward the tip, and leaves thediffused section less filled. Thus, the air exits the film cooling holeat a greater velocity, and does not stay on the face of the blade aslong as would be desired.

SUMMARY OF THE INVENTION

In a disclosed embodiment of this invention, the meter section of filmcooling holes in a turbine blade extend with a major component in adirection from the blade tip toward the blade root. A diffused sectionis formed to enlarge a film cooling hole at the outer face of the blade.The diffused section extends toward the blade tip from the metersection.

As the blade rotates, and cooling air exits the film cooling hole,centrifugal force forces some of the cooling air into the diffusedsection and the diffused section is relatively full compared to theprior art. Thus, the air exits the film cooling hole at a lower velocitythan in the prior art, tends to stay on the face of the turbine bladelonger, and cover a greater surface area.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a gas turbine engine.

FIG. 2A is a view of a prior art turbine blade.

FIG. 2B is an enlarged view of a portion of the FIG. 2A turbine blade.

FIG. 2C is another view of the FIG. 2A blade.

FIG. 3 is a view similar to FIG. 2C, but showing the inventive blade.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A gas turbine engine 10 circumferentially disposed about an enginecenterline, or axial centerline axis 12 is shown in FIG. 1. The engine10 includes a fan 14, a compressor 16, a combustion section 18 and aturbine 11. As is well known in the art, air compressed in thecompressor 16 is mixed with fuel and burned in the combustion section 18and expanded in turbine 11. The turbine 11 includes rotors 22 whichrotate in response to the expansion, driving the compressor 16 and fan14. The turbine 11 comprises alternating rows of rotary airfoils orblades 24 and static airfoils or vanes 26. In fact, this view is quiteschematic, and blades 24 and vanes 26 are actually removable. It shouldbe understood that this view is included simply to provide a basicunderstanding of the sections in a gas turbine engine, and not to limitthe invention. This invention extends to all types of turbine enginesfor all applications.

FIG. 2A shows a prior art turbine blade 24. As known, a platform 32 andblade root form a base for an airfoil 34. The airfoil 34 includes aplurality of film cooling holes 36. As can be appreciated, the holes 36are formed on the pressure side 198 of the turbine blade. The holes arein an array, with holes being spaced in several columns and rowsextending between the root of the airfoil and the tip, and from thetrailing edge 197 toward the leading edge 199. As an example, there areseveral columns 200, 201, and 202 spaced between the trailing edge 197and the leading edge 199. In addition, there are holes 202 that arecloser to the root than other holes 205 or 207.

As shown in FIG. 2B, the film cooling holes 36 have a meter section 38,and a diffused section 40.

As shown in FIG. 2C, the meter section 38 extends along a non-parallelangle relative to a radial axis, and with a component extending from theblade root to the blade tip. The air from an internal cooling passage 42passes through this meter section 38 to an outer face of the airfoil 34.As can be seen in FIG. 2C, this diffused section extends from the metersection 38 and closer to the blade root than the blade tip. Now, as theturbine blade 24 rotates, centrifugal forces force air from the metersection 38 radially outwardly, and away from the diffused section 40.Thus, the diffused section 40 is not always filled.

As shown in FIG. 3, in an inventive turbine blade 50, a meter section 52extends with a main component of its direction from the blade tip to theblade root. A diffused section 54 extends toward the blade tip from themeter section 52. As can be seen, the diffused section 54 may be at anangle having a lesser component in the direction from the tip towardsthe root. As can be appreciated from FIG. 2, the enlarged portions 40and 54 may not extend directly, or solely, towards the root and tiprespectively. Still, they extend with a major component in thosedirections. As is clearly shown in FIG. 3, the meter sections 52 extendfrom cooling passage 42 at an angle that is initially from the blade tiptoward the blade root, and at a single angle to an outer face of theairfoil. While holes 52 are shown along a single column, it should beappreciated that these holes would be utilized in an array such as shownin FIG. 2A or 2B.

When centrifugal force acts on the air in the meter section 52, the airis driven into the diffused section 54. Flow momentum will ensure thatthe meter section 52 is still full. Thus, the present invention ensuresthe cooling air is delivered to the outer face 51 across the entirety ofthe film cooling holes. As can be appreciated from FIG. 2B, the diffusedsections 40 and 54 may not extend directly, or solely, towards the rootand tip respectively. Still, they extend with a major component in thosedirections. It should be noted that the flow in the internal coolingpassage 42 can flow in any direction and does not necessarily have toflow from blade root to blade tip.

In fact, the meter section can extend in the reverse direction or anydirection with the diffused section extending toward the tip. Flowmomentum will still fill the meter section while centrifugal force willfill the diffused section.

Although a preferred embodiment of this invention has been disclosed, aworker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

1. A turbine blade comprising: a root, and an airfoil extending awayfrom the root to a tip; a plurality of film cooling holes on an outerface of the airfoil, said airfoil having at least one internal coolingpassage for receiving air from a source, and delivering air to said filmcooling holes; and said film cooling holes receiving air from saidcooling passage through meter sections extending with a component in adirection from the tip towards the root.
 2. The turbine blade as setforth in claim 1, wherein a diffused section of an outer end of saidfilm cooling holes extending towards said tip from said meter section.3. The turbine blade as set forth in claim 2, wherein said diffusedsection is formed along an angle having a lesser component in thedirection from said tip toward said root than said meter section.
 4. Theturbine blade as set forth in claim 2, wherein said meter sectionsextend at a first angle, with an extension of said meter sectionextending through to an outer wall of said airfoil, and said diffusedsection extending at a different angle than said meter section.
 5. Theturbine blade as set forth in claim 1, wherein said plurality of filmholes being formed in an array, with there being film holes spaced atdifferent locations in a direction between a trailing edge and a leadingedge of the airfoil, and also at different locations between the rootand the tip of the airfoil.
 6. The turbine blade as set forth in claim1, wherein said meter section extends from said cooling passageinitially at said direction.
 7. The turbine blade as set forth in claim10, wherein said meter section extends along a single angle from saidcooling passage to said outer wall of said outer face of the airfoil. 8.The turbine blade as set forth in claim 1, wherein said array of coolingholes is formed on a pressure side of said airfoil.
 9. A turbine bladecomprising: a root, and an airfoil extending away from the root toward atip; a plurality of film cooling holes on an outer face of said airfoil,said airfoil having at least one internal cooling passage for receivingair from a source, and delivering air to said film cooling holes; andsaid film cooling holes receiving air from said internal cooling passagethrough meter sections, and an diffused section of an outer end of saidfilm cooling holes communicates with said meter section, said diffusedsection extending towards said tip from said meter section.
 10. Theturbine blade as set forth in claim 9, wherein said diffused section isformed along an angle having a lesser component in the direction fromsaid tip toward said root than said meter section.
 11. The turbine bladeas set forth in claim 9, wherein said meter section extends from saidcooling passage initially at said direction.
 12. The turbine blade asset forth in claim 11, wherein said meter sections each extend along asingle angle from said cooling passage to said outer wall of said outerface of the airfoil.
 13. The turbine blade as set forth in claim 9,wherein said array of cooling holes is formed on a pressure side of saidairfoil.